High-current field emission from a vertically aligned carbon nanotube field emitter array

Arrays of vertically aligned carbon nanotubes (CNTs) were grown on a patter ned sputtered cobalt film by chemical vapor deposition from ethylenediamine at 900 degreesC. Each square array comprises a moderate density of nanotub es with an average height of 90 mum covering a total area of 3.6x10(-3) cm( 2). Field emission measurements were carried out on individual arrays at pr essures below 10(-8) mbar. The spacing between the anode and the top of the CNT array is 935 mum and a total current of 2 mA could be obtained at 2.5 kV. A Fowler-Nordheim plot of the I-V data shows an unusually high field en hancement factor at lower fields. At an average field strength of 1.925 V/m um, the corresponding emission current density is 130 mA/cm(2). This emissi on current was found to be very stable, with short-term fluctuations (5 Hz measurement bandwidth) of no more than +/-1.5%, while the current drifted l ess than 1.5% over a test period of 20 h. (C) 2001 American Institute of Ph ysics.